Data from: Enhanced aphid abundance in spring desynchronizes predator–prey and plant–microorganism interactions

Climate change leads to phenology shifts of many species. However, not all species shift in parallel, which can desynchronize interspecific interactions. Within trophic cascades, herbivores can be top–down controlled by predators or bottom–up controlled by host plant quality and host symbionts, such as plant-associated micro-organisms. Synchronization of trophic levels is required to prevent insect herbivore (pest) outbreaks. In a common garden experiment, we simulated an earlier arrival time (~2 weeks) of the aphid Rhopalosiphum padi on its host grass Lolium perenne by enhancing the aphid abundance during the colonization period. L. perenne was either uninfected or infected with the endophytic fungus Epichloë festucae var. lolii. The plant symbiotic fungus produces insect deterring alkaloids within the host grass. Throughout the season, we tested the effects of enhanced aphid abundance in spring on aphid predators (top–down) and grass–endophyte (bottom–up) responses. Higher aphid population sizes earlier in the season lead to overall higher aphid abundances, as predator occurrence was independent of aphid abundances on the pots. Nonetheless, after predator occurrence, aphids were controlled within 2 weeks on all pots. Possible bottom–up control of aphids by increased endophyte concentrations occurred time delayed after high herbivore abundances. Endophyte-derived alkaloid concentrations were not significantly affected by enhanced aphid abundance but increased throughout the season. We conclude that phenology shifts in an herbivorous species can desynchronize predator–prey and plant–microorganism interactions and might enhance the probability of pest outbreaks with climate change.

气候变化可导致诸多物种的物候发生偏移。然而，并非所有物种的物候偏移均同步，这会破坏种间相互作用的同步性。在营养级联（trophic cascades）效应中，植食动物可受到捕食者的下行控制（top-down control），或受宿主植物品质与宿主共生体（如植物相关微生物）的上行控制（bottom-up control）。维持营养级的同步性是防控植食性昆虫（害虫）暴发的必要条件。本研究开展同质园（common garden）实验，通过在定殖期提升蚜虫种群密度，模拟了禾谷缢管蚜（Rhopalosiphum padi）提前约2周抵达其宿主禾草多年生黑麦草（Lolium perenne）的场景。供试的多年生黑麦草分为未感染与感染内生真菌（endophytic fungus）香柱菌Lolii变种（Epichloë festucae var. lolii）两组；该植物共生真菌可在宿主禾草体内合成具有驱虫作用的生物碱（alkaloids）。本研究在整个生长季中，探究了春季蚜虫种群密度升高对蚜虫捕食者（下行调控通路）与禾草-内生真菌共生体（上行调控通路）的影响。由于试验盆中的捕食者出现与否与蚜虫种群密度无关，因此生长季前期更高的蚜虫种群数量会导致整体蚜虫丰度升高。尽管如此，在捕食者出现后，所有试验盆中的蚜虫均在2周内得到了控制。内生真菌浓度升高对蚜虫产生的潜在上行控制效应，在植食动物种群密度升高后出现了时间延迟。内生真菌合成的生物碱浓度并未因蚜虫种群密度升高而产生显著变化，但在整个生长季中持续升高。本研究结论表明，植食动物物种的物候偏移可破坏捕食者-猎物与植物-微生物相互作用的同步性，并可能在气候变化背景下提升害虫暴发的概率。